605. Gibberellic acid. Part XII. The stereochemistry of allogibberic acid

Abstract

Allogibberic acid and epiallogibberic acid, stereoisomeric degradation products of gibberellic acid, are shown to have the absolute configurations (111) and (XX) respectively.GIBBERELLIC ACID 1 (I), on treatment with dilute mineral acid, yields 233 allogibberic acid 4 (111). Allogibberic acid has also been obtained by heating gibberellic acid with water, and from 2,7-dihydroxy-l-methyl-S-methylene-lOa~-gibba-3,4a(4b) -diene-1 ,lo-dicarboxylic acid t (gibberellenic acid 19596) (11) with boiling water or cold mineral acid.* Part XI, J . Sci. Food Agric., in the press.t By agreement with the Editor the name gibbane is used for the fully saturated tetracyclic systemThe ring system derived from gibbane by inversion at positions 7 and 9a is called

A ring-distortion strategy to construct stereochemically complex and structurally diverse compounds from natural products

“…Gibberellic acid contains a tetracyclic diterpene core with a fused lactone, two allylic alcohols, an exocyclic olefin, and a carboxylic acid, enabling selective and independent functionalization of each ring of the core structure via a variety of ring system distortion reactions. We have exploited these structural features in concert with known degradation reactions of G 24–27 in the construction of complex and diverse scaffolds in three to five steps from gibberellic acid (Figure 2, G1–G6 ).…”

“…Hydrazine-promoted elimination of the lactone on G , 27 followed by methylation and acetylation, affords triene G7 . Treatment with m CPBA yields an intermediate epoxide with complete selectivity for the tetrasubstituted olefin which, when subjected to oxidative cleavage conditions using PCC, produces diketone G1 .…”

Confirmation of structure and synthesis of three new 11β-OH C20 gibberellins from loquat fruit

“…As outlined in Scheme 3, the preparation of a suitable analogue of diazoketone 11 began with the 7-methyl ester (18) of gibberellenic acid (17). Gibberellenic acid is readily prepared from GA 3 (1) in 37% yield by heating with hydrazine hydrate.…”

“…Gibberellenic acid is readily prepared from GA 3 (1) in 37% yield by heating with hydrazine hydrate. 18 However, so that we could discriminate between the two carboxyl functions, we had previously treated GA 3 methyl ester (16) under equivalent conditions and had obtained the desired mono-ester 18 in only 23% yield. 19 Fortunately, through the simple expedient of using hydrazine monohydrochloride in DMF, we were able to elevate the yield to 39% (56% net, based on recovered starting material).…”

The chemistry of the gibberellins

“…It occurs during bromination with trimethylphenylammonium perbromide under very dry Gibberellenic acid (56), allogibberic, and 9-epiallogibberic acid (60) are also obtained by the decomposition of gibberellic acid (2) with hydrazine hydrate at 1 50°. 99 In the saturated series, the epimerization by dilute alkali of …”